1. Field of the Invention
The invention relates to the field of controlling of the length and depth of a metal cutting operation being carried out by a cutting torch. In addition, the invention relates to the field of guiding a cutting torch to cut an accurately controlled thickness of metal from the surface of a hollow workpiece in connection with the removal of the workpiece from another structure extending therethrough.
2. Description of the Prior Art
U.S. Pat. No. 2,432,240, which issued on Dec. 9, 1947, discloses a portable apparatus for controlling a cutting torch to cut a metal beam. The apparatus of this patent is constructed to make a cut extending at right angles to the surface of the beam in order to cut completely through the beam.
U.S. Pat. No. 2,061,442, which issued on Nov. 17, 1936, and U.S. Pat. No. 2,594,151, which issued on Apr. 22, 1952, show devices adapted to be clamped to cylindrical workpieces such as pipes. These devices cut at substantially a right angle to the surface of the pipe and cut completely through the pipe about its periphery.
U.S. Pat. No. 2,152,213, which issued on Mar. 28, 1939, discloses a device for controlling a torch to cut away an outer portion of a plate to which the apparatus is attached. The device includes the construction for advancing the torch along the length of the plate.
U.S. Pat. No. 2,125,178, which issued on July 26, 1938, discloses an apparatus upon which a solid cylindrical workpiece such as a billet is mounted. The apparatus is adapted to condition the surface of the billet by a torch as the billet is rotated with respect to the torch.